From 3801c0f6759593c897833004f1be1d6e8a655780 Mon Sep 17 00:00:00 2001
From: Alex Rozgo <alex.rozgo@gmail.com>
Date: Sat, 24 Jun 2017 17:07:39 -0700
Subject: [PATCH] Fix #34 - deterministic_randomness test failures adds
 deterministic distribution functions for randutils fixes shuffle to do
 deterministic shuffling adds deterministic_distributions tests

---
 .../include/eos/utilities/randutils.hpp       | 24 +++++++-----
 tests/tests/misc_tests.cpp                    | 37 +++++++++++++++++--
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/libraries/utilities/include/eos/utilities/randutils.hpp b/libraries/utilities/include/eos/utilities/randutils.hpp
index 0d0ae008a06..2c8c00eaa14 100644
--- a/libraries/utilities/include/eos/utilities/randutils.hpp
+++ b/libraries/utilities/include/eos/utilities/randutils.hpp
@@ -102,6 +102,9 @@
 #include <thread>
 #include <algorithm>
 
+#include <boost/random/uniform_int_distribution.hpp>
+#include <boost/random/uniform_real_distribution.hpp>
+
 // Ugly platform-specific code for auto_seeded
 
 #if !defined(RANDUTILS_CPU_ENTROPY) && defined(__has_builtin)
@@ -572,8 +575,8 @@ using auto_seed_256 = auto_seeded<seed_seq_fe256>;
 template <typename Numeric>
 using uniform_distribution = typename std::conditional<
             std::is_integral<Numeric>::value,
-              std::uniform_int_distribution<Numeric>,
-              std::uniform_real_distribution<Numeric> >::type;
+              boost::random::uniform_int_distribution<Numeric>,
+              boost::random::uniform_real_distribution<Numeric> >::type;
 
 
 
@@ -730,16 +733,19 @@ class random_generator {
                            std::forward<Params>(params)...);
     }
 
-    template <typename Iter>
-    void shuffle(Iter first, Iter last)
-    {
-        std::shuffle(first, last, engine_);
-    }
-
     template <typename Range>
     void shuffle(Range&& range)
     {
-        shuffle(std::begin(range), std::end(range));
+        // Fisher-Yates shuffle algorithm
+        int idx_count = range.size();
+        for (auto idx = range.rbegin(); idx != range.rend() - 1; ++idx , --idx_count)
+        {
+            int rand_idx = uniform(0, idx_count - 1);
+            if (*idx != range.at(rand_idx))
+            {
+                std::swap(range.at(rand_idx), *idx);
+            }
+        }
     }
 
 
diff --git a/tests/tests/misc_tests.cpp b/tests/tests/misc_tests.cpp
index 4bb8ad3c64a..9f9daaf5271 100644
--- a/tests/tests/misc_tests.cpp
+++ b/tests/tests/misc_tests.cpp
@@ -49,12 +49,43 @@ BOOST_AUTO_TEST_CASE(deterministic_randomness)
    vector<string> words = {"infamy", "invests", "estimated", "potters", "memorizes", "hal9000"};
    rng.shuffle(words);
    BOOST_CHECK_EQUAL(fc::json::to_string(words),
-                     fc::json::to_string(vector<string>{"potters","hal9000","memorizes","infamy","invests","estimated"}));
+                     fc::json::to_string(vector<string>{"hal9000","infamy","estimated","memorizes","invests","potters"}));
    rng.shuffle(words);
-   BOOST_CHECK_EQUAL(fc::json::to_string(words),
-                     fc::json::to_string(vector<string>{"memorizes","hal9000","infamy","invests","estimated","potters"}));
+   BOOST_CHECK_EQUAL(fc::json::to_string(words), 
+                     fc::json::to_string(vector<string>{"hal9000","estimated","infamy","memorizes","potters","invests"}));
+} FC_LOG_AND_RETHROW() }
+
+BOOST_AUTO_TEST_CASE(deterministic_distributions)
+{ try {
+   randutils::seed_seq_fe<1> seed({123454321});
+   randutils::random_generator<pcg32_fast> rng(seed);
+
+   std::vector<int> nums = {0, 1, 2};
+
+   BOOST_CHECK_EQUAL(rng.uniform(0.0, 1.0), 0.52802440151572227);
+   BOOST_CHECK_EQUAL(rng.uniform(0.0, 1.0), 0.36562641779892147);
+   BOOST_CHECK_EQUAL(rng.uniform(0.0, 1.0), 0.44247416267171502);
+
+   BOOST_CHECK_EQUAL(rng.pick(nums), 2);
+   BOOST_CHECK_EQUAL(rng.pick(nums), 0);
+   BOOST_CHECK_EQUAL(rng.pick(nums), 2);
+
+   rng.shuffle(nums);
+   std::vector<int> a{0, 1, 2};
+   BOOST_CHECK(std::equal(nums.begin(), nums.end(), a.begin()));
+   rng.shuffle(nums);
+   std::vector<int> b{0, 2, 1};
+   BOOST_CHECK(std::equal(nums.begin(), nums.end(), b.begin()));
+   rng.shuffle(nums);
+   std::vector<int> c{1, 0, 2};
+   BOOST_CHECK(std::equal(nums.begin(), nums.end(), c.begin()));
+
+   BOOST_CHECK_EQUAL(rng.uniform(0, 9), 2);
+   BOOST_CHECK_EQUAL(rng.uniform(0, 9), 9);
+   BOOST_CHECK_EQUAL(rng.uniform(0, 9), 0);
 } FC_LOG_AND_RETHROW() }
 
+
 BOOST_AUTO_TEST_SUITE_END()
 
 } // namespace eos